ADU rules in Hamilton County, IN — also called accessory dwelling unit regulations or granny flat ordinances — cover setbacks, owner-occupancy, parking, and permit requirements.
Hamilton County's fast-growing cities zone their own land under IC 36-7-4, so ADU rules come from Carmel, Fishers, Westfield, or Noblesville, not the county. Carmel allows one guest house with cooking facilities only on lots of at least one acre.
Indiana is a home-rule-of-zoning state: cities and towns zone through their own plan commissions under IC 36-7-4, while the Hamilton County Plan Commission zones only unincorporated land. Because nearly all residents live in Carmel, Fishers, Westfield, or Noblesville, whether an accessory dwelling unit or in-law suite is allowed depends on your city's Unified Development Ordinance (UDO), not county government. Carmel's UDO does not permit general backyard ADUs; instead, under Section 5.02(C)(4), one guest house with cooking facilities is allowed only as an accessory building on lots of at least one acre. Any dwelling unit must also meet the Indiana Residential Code (675 IAC 14). Confirm ADU eligibility with your city's community-development department first.
Building or renting an ADU not allowed under your city's UDO is a local zoning violation, enforced by Carmel, Fishers, Westfield, or Noblesville code enforcement, not the county. Fines and removal orders are set by local ordinance.
Other ordinances people look up for this city. Green dot = verified primary-source excerpt.
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See how Hamilton County's adu rules rules stack up against other locations.
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